Method of producing a carburizing gas



9, 1940. F. D. WIDNER 2,186,690

IIETHOD 0F PRODUCING A CARBURIZINQ G AS Filed July 8, 1957 3nnentor ED. W/"aner (Ittorneg Patented i... 9, 1940 PATENT OFFICE 2,186,690 METHOD or raom czn m a cmumzma Franklin D. Widner, Toledo, ohm.

Surface Combustion Corporation, Ohio, a corporation of New York assigior to Toledo,

Application July 8, 1937, Serial No. 152,626

.3 calmin (01. 148-11)} This invention relates to the art of carburizing steel articles to make them resistant to wear.

It is known that the articles may be carburized by exposing them while in a heated condition to a gaseous atmosphere comprising a mixture .of charcoal gas and natural gas.

In districts where natural gas is not available,

it is customary to use bottled gases, such as, propane and butane, for enriching the charcoal gas. However, when a hydrocarbon gas other than pure natural gas is simply added to the charcoal gas, it invariably happens that when the articlesare removed from the carburizing retort, they will be found to be coated with a tightly adhering scale having the appearance of an oxide scale but which on analysis .is found to be a hard and dense coating of coke-like material which is metallic in appearance. Such coating interferes with normal carburization and frequently prevents it entirely.

The object of the present invention is to provide an improved method of utilizing the higher hydrocarbons and more particularly commercial propane and butane for enriching charcoal gas in such a way that articles may be carburized without the formation of the objectionable coatingabove referred to. g Y

In accordance with the present invention, the

charcoal gas is enriched by flowing a stream of hydrocarbon gas into the incandescent charcoal of a charcoal gas producer. By thus enriching the charcoal gas, it may be utilized without any further treatment as a carburizing gas. and articles carburized in such a gas will be devoid of the objectionable coating above referred to.

For a more complete understanding 'of the invention, reference is made to the detailed description taken in connection with the accompanying drawing, wherein the single figure shows a more or less diagrammatic layout of the carburizing apparatus as a whole. I indicates-a carburizing retort in a furnace 2 having a heating chamber 3 into which a plu-' rality of burners 4 fire-for heating the articles in the retort to carburizing temperature. 5 indicates a pipe for supplying carburizing gas to the retort and 6 a vent through which spent gases leave the retort.

It indicates an upright tubular charcoal retort in a heating chamber ll into which a plurality of burners l2 fire for heating the charcoal l3 in 'the' retort to incandescence. Ordinarily the temperaturein the heating chamber II will be maintained at approximately l6001800 F. The retort extends through the roof ll of the heatingchamber and has a charcoal hopper l5 at its upper'end, the top of the hopper being normally sealed by a removable cover It. The gases produced in the retort pass therefrom bv way of a pipe I! 'shown as within the retort adjacent its .upper end. The pipe extends out of the retort connects'with a suction pump l8, the discharge side ofwhich delivers to the pipe 5 leading to the carburizing retort l. is delivered to the lower end of the charcoal retort by a pipei9 having a control valve 20.

The lower end of the retort l0 restson a base 2| which constitutes the bottom of the heating chamber II. This base has a vertical chamber 22, the top of which is in open communication with the lower end of the retort and the column of charcoal in the retort extends down into said chamber. The lower end of the chamber hasa downwardly extending chute 23 which dips into an ash pan- 24 adapted to contain a sealing liquid, such as water, for sealing off the lower end of the chute. Ashes resulting from the operation of the gas producer areraked out of the. pan as circumstances require.

The hydrocarbon gas above the roof I of the heating chamber andindicates a pipe for supplying air to the in, the gases of combustion flowing upwardly into the retort ill for further reaction therein. It is preferred that some fuel gas be admixed with the air whereby to reduce the consumption of the As already stated, the heating chamber II will be maintained at a temperature of approximately 1600-l800 F. The reason for withdrawing the gases from the retort at a point below the roof I of the heating chamber is to prevent the freshly formed carbon monoxide from reacting with relatively cool charcoal to the production of' CO2. By flowing the hydrocarbon gas into the retort l0, its composition is so changed that the gases coming from the retort may be used without further treatment for carburizing articles in the carburizing retort I. In this connection it should be stated that-the gases coming from the charcoal retort have a dew point below 25 F. and, therefore, need not bedehydrated before delivering to the carburizing retort I.

obtained chamber 22 for burning with the charcoal therenitrogen and the dew point of the gases being below 25 F. 1

For the purposes of comparison,-the kind of gas obtained when no hydrocarbon was flowed into the retort the following is cited: 31% CO; 0.1%

C 1% CH4; 11% Hz; the balance being nitrogen and the dew point'of the gases being less than 25 F. V The important differences between the two kinds of gases as regards carburizing operation is the difierence' in methane content.

The kind of hydrocarbon-gas that is flowed into the retort I0 is of more or less secondary importance, since in any event it will be broken down in contact with the incandescent charcoal and yield methane'which is the gas that is desired. Thus natural gas that is not pure methane may advantageously be flowed through the retort for the removal of impurities. However, it is with the treatment of the higher hydrocarbons like butane and propane and mixtures of these containing propylene or butylene that the invention has special utility .since it is with the higher hydrocarbons that trouble is encountered when they are simply added to a weak carburizing gas such as charcoal gas to form a stronger carburizing gas.

What I claim is:

1. That method of utilizing a hydrocarbon gas to produce a, carburizing gas for carburizing steel mosphere for said articles.

' 2;That method of utilizing a hydrocarbon gas to produce a carburizing gas for carburizing steel articles which comprises first reacting said hydrocarbon'gas with incandescent charcoal, ad- Mixing the gaseous products of such reaction with charcoal gas, and then utilizing the resulting mixture as an atmosphere for said articles.

3.. That method of utilizing a hydrocarbon gas to produce a carburizing gas for carburizing steel articleswhich comprises first reacting said bydrocarbon gas with incandescent charcoal in a retort, admixing with the gaseous products of such reaction while in said retort a diluent comprising carbon monoxide, and then withdrawing the resulting mixture of gases from said retort and utilizing the same as an atmosphere for said articles.

FRANKLIN D. WIDNER. 

